Fantasy About My Wife

I am obsessed with a certain fantasy regarding my very sexy wife. She is in her 50's, but looks great, and although she is modest and conservative out in the world, she is very sensual behind closed doors.
I constantly fantasize about watching her having sex with a young, black stud. I picture her on our bed, legs spread wide, as his stiff cock slides in and out of her. I imagine her moaning, and squeezing his ass, pulling him into her. I always see her in her red lingerie, with her big beautiful tits bouncing behind the shear fabric. I'm hard just writing this! He would then fuck her from behind, so I could look into her eyes as she's being stuffed with his big cock. I always think about him finishing off into her mouth, his cum flowing out, down her chin, dripping onto her tits.
I have thought about this as I fuck her, but then I cum to quickly!